Toroidal printed coil

ABSTRACT

A toroidal printed coil includes a plurality of annular holes ( 2 ) and a plurality of center holes ( 3 ) surrounded by the annular holes ( 2 ) in an insulating substrate ( 1 ). A plurality of annular juts ( 4 ), each comprising a portion surrounded by the annular hole ( 2 ) and the center hole ( 3 ), are formed. A printed coil sheet having a plurality of toroidal printed coils, in which a conductor film ( 6 ) is spirally formed at front-and-rear surfaces and side surfaces of annular portions ( 5 ) of the annular juts ( 4 ) with each annular portion taken as an axis, is obtained. With this printed coil sheet, a plurality of toroidal printed coils (P) are obtained by cutting the insulating substrate ( 1 ) off from the individual annular juts ( 4 ).

FIELD OF THE INVENTION

The present invention relates to a toroidal printed coil manufacturingmethod as well as to a toroidal printed coil manufactured by themanufacturing method. The toroidal printed coil manufacturing methodaccording to the present invention is suited for manufacturing aplurality of toroidal printed coils simultaneously, and a printed coilsheet to be used in the processes of the manufacturing method can alsobe used as a printed wiring board having a plurality of toroidal printedcoils. Toroidal printed coils obtained by the present invention are usedas inductance devices, antennas, solenoid coils, motor coils and thelike.

BACKGROUND OF THE INVENTION

A printed coil manufacturing method according to the prior art isdescribed with reference to FIG. 8.

There has been known a coil manufacturing method comprising thefollowing steps. That is, as shown in FIG. 8, long, narrow and linearthrough slits 11, at least two in number, are formed in an insulatingsubstrate 10 so as to be opposite to one another with a specifiedspacing. Metal layers are formed at front and rear surfaces of theinsulating substrate 10 as well as inner surfaces of the through slits11. The metal layers of the front and rear surfaces of the insulatingsubstrate 10 except portions 16 forming a plurality of coil wires areremoved, and the insulating substrate 10 is cut at cutting lines A, B,C, and D along the through slits 11. Then, in the cutting sections,except connection-use metal layers for individually interconnecting themetal layers of coil-wire forming portions of the front and rearsurfaces of the insulating substrate 10, the metal layers of the innersurfaces of the through slits are removed. Therefore, the metal layersof the front and rear surfaces of the insulating substrate 10 areconnected spirally to one another, by which coils are manufactured(Japanese Laid-Open Patent Publication No. 59-103321).

However, this m method has a large number of manufacturing steps and iscomplex, due to the steps of forming metal layers forming a plurality ofcoil wires at the front and rear surfaces of the insulating substrate aswell as the inner surfaces of the through slits, then cutting theinsulating substrate along the through slits, and thereafter furtherconnecting the metal layers of the front and rear surfaces of theinsulating substrate to one another spirally.

Accordingly, an object of the present invention is to solve theaforementioned issues and to provide a toroidal printed coilmanufacturing method which allows toroidal printed coils to bemanufactured with great simplicity without requiring much time andlabor, and to provide a toroidal printed coil manufactured by thismanufacturing method.

SUMMARY OF THE INVENTION

In order to achieve the above object, the present invention has thefollowing constitutions.

According to a first aspect of the present invention, there is provideda toroidal printed coil manufacturing method for simultaneouslymanufacturing a plurality of toroidal printed coils including aplurality of annular holes, a plurality of center holes, and annularjuts formed on an insulating substrate. The annular juts are formed of aplurality of annular portions surrounded by the plurality of annularholes and the plurality of center holes surrounded by these annularholes. Each annular portion is taken as an axis, forming a conductorfilm at front-and-rear surfaces and inner-and-outer side surfaces of theannular portion simultaneously and spirally.

According to a second aspect of the present invention, there is providedthe toroidal printed coil manufacturing method according to the firstaspect, wherein the plurality of annular holes and the plurality ofcenter holes surrounded by these annular holes are formed in theinsulating substrate prior to forming the conductor film.

According to a third aspect of the present invention, there is providedthe toroidal printed coil manufacturing method according to the first orsecond aspect, wherein for the formation of the conductor film, after aplating resist layer is formed and patterned at portions of thefront-and-rear surfaces and the inner-and-outer side surfaces other thanportions to be left as the conductor film, plating process is performedso that the conductor film is formed at the portions to be left as theconductor film.

According to a fourth aspect of the present invention, there is providedthe toroidal printed coil manufacturing method according to the first orsecond aspect, wherein for the formation of the conductor film, afterthe conductor film is formed generally entirely at the front-and-rearsurfaces and inner-and-outer side surfaces of the annular jut,unnecessary portions of the generally entirely formed conductor film areremoved by irradiation of a laser beam or the like so that the conductorfilm is formed at only necessary portions.

According to a fifth aspect of the present invention, there is providedthe toroidal printed coil manufacturing method according to the first orsecond aspect, wherein for the formation of the conductor film, afterthe conductor film is formed generally entirely at the front-and-rearsurfaces and inner-and-outer side surfaces of the annular jut, anetching resist layer is formed and patterned at portions to be left asthe conductor film, unnecessary portions of the generally entirelyformed conductor film are removed by etching so that the conductor filmis formed at only necessary portions.

According to a sixth aspect of the present invention, there is providedthe toroidal printed coil manufacturing method according to any one ofthe first, second, and fifth aspects, further comprising preparing acopper-clad laminate in which a copper foil is cladded on front and rearsurfaces of the insulating substrate. The center holes are formedthrough the insulating substrate and the annular holes are formed sothat the annular portion of each annularjut has a specified width and sothat a portion for connecting with the other portion of the insulatingsubstrate is left, by which the plurality of annular juts are formed.Copper plating is generally formed entirely at the front-and-rearsurfaces and inner-and-outer side surfaces of the annular portion ofeach annular jut. Etching resist is formed congruous with the spiralconductor film with the annular portion of the annular jut taken as anaxis. Unnecessary portions of the generally entirely formed conductorfilm are then removed, by etching, where the etching resist has not beenformed. The etching resist is thereafter flaked off from the insulatingsubstrate, by which the conductor film is obtained.

According to a seventh aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to anyone of the first to sixth aspects, further comprising forming terminalsof start and end portions of the spiral conductor film at the connectingportion and in the same plane by etching. Portions of the coil terminalportions other than copper-foil portions are coated, with solder resist,to thereby insulate those portions, and then the connecting portion iscut, by which the plurality of toroidal printed coils are obtained.

According to an eighth aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to anyone of the first to seventh aspects, wherein each of the center holes iscircular shaped and a perimeter of the annular portion of the annularjut has a circular shape concentric with the center hole.

According to a ninth aspect of the present invention, there is providedthe toroidal printed coil manufacturing method according to any one ofthe first to eighth aspects, wherein each of the center holes ispolygonal-shaped and a perimeter of the annular portion of the annularjut has a polygonal shape similar to the center hole.

According to a tenth aspect of the present invention, there is providedthe toroidal printed coil manufacturing method according to any one ofthe first to ninth aspects, wherein the conductor film is uniform inwidth.

According to an eleventh aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to anyone of the first to tenth aspects, wherein the conductor film isnonuniform in width.

According to a twelfth aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to anyone of the first to eleventh aspects, wherein the individual annularjuts are cut off from the insulating substrate, whereby the plurality oftoroidal printed coils are obtained.

According to a thirteenth aspect of the present invention, there isprovided a toroidal printed coil manufactured by the toroidal printedcoil manufacturing method according to any one of the first to twelfthaspects.

According to a fourteenth aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to thethird aspect, wherein the process for patterning the plating resistlayer comprises using a photo-curable photoresist film to form theplating resist layer, and exposing to light one surface of the annularportion on which a ninth mask and a light control sheet are stacked. Theninth mask behaves so as to inhibit light transmission at front-surfacepattern forming portions where a conductor film of a front surface ofthe annular portion is to be formed with the annular portion taken as anaxis, to inhibit light transmission at side-portion pattern formingportions where conductor films of outer-and-inner side surfaces of theannular portion are to be formed with the annular portion taken as anaxis, and to permit light transmission at the other portions. The lightcontrol sheet behaves so as to make incident light scattered orrefracted and given off from a side opposite to the incident side. Theother surface of the annular portion on which a tenth mask and a lightcontrol sheet are stacked are also exposed to light. The tenth maskbehaves so as to inhibit light transmission at rear-surface patternforming portions where a conductor film of a rear surface of the annularportion is to be formed with the annular portion taken as an axis, toinhibit light transmission at side-portion pattern forming portionswhere conductor films of outer-and-inner side surfaces of the annularportion are to be formed with the annular portion taken as an axis, andto permit light transmission at the other portions. The light controlsheet behaves so as to make incident light scattered or refracted andgiven off from a side opposite to the incident side, thus allowing onlythe exposed portions of the photoresist film to be cured. Thereafter,the photoresist film is developed to thereby remove uncured portionsother than the cured portions, so that the plating resist layer isformed at each of the portions other than the portions where theconductor film of the front surface of the annular portion with theannular portion taken as an axis, the conductor film of the rear surfaceof the annular portion with the annular portion taken as an axis, andthe conductor films of the outer-and-inner side surfaces of the annularportion with the annular portion taken as an axis are to be formed.

According to a fifteenth aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to thethird aspect, wherein the process for patterning the plating resistlayer comprises using a photo-degradable photoresist film to form theplating resist layer, and exposing to light one surface of the annularportion on which an eleventh mask and a light control sheet are stacked.The eleventh mask behaves so as to permit light transmission atfront-surface pattern forming portions where a conductor film of a frontsurface of the annular portion is to be formed with the annular portiontaken as an axis, to permit light transmission at side-portion patternforming portions where conductor films of outer-and-inner side surfacesof the annular portion are to be formed with the annular portion takenas an axis, and to inhibit light transmission at the other portions. Thelight control sheet behaves so as to make incident light scattered orrefracted and given off from a side opposite to the incident side. Theother surface of the annular portion on which a twelfth mask and a lightcontrol sheet are stacked are also exposed to light. The twelfth maskbehaves so as to permit light transmission at rear-surface patternforming portions where a conductor film of a rear surface of the annularportion is to be formed with the annular portion taken as an axis, topermit light transmission at side-portion pattern forming portions whereconductor films of outer-and-inner side surfaces of the annular portionare to be formed with the annular portion taken as an axis, and toinhibit light transmission at the other portions. The light controlsheet behaves so as to make incident light scattered or refracted andgiven off from a side opposite to the incident side, thus allowing onlythe exposed portions of the photoresist film to be photo-degraded.Thereafter, the photoresist film is developed to thereby remove only thephoto-degraded portions, so that the plating resist layer is formed ateach of portions other than the portions where the conductor film of thefront surface of the annular portion with respect to the annular axis ofthe annular portion, the conductor film of the rear surface of theannular portion with respect to the annular axis of the annular portion,and the conductor films of the outer-and-inner side surfaces of theannular portion with respect to the annular axis of the annular portionare to be formed.

According to a sixteenth aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to thethird aspect, wherein the process for patterning the plating resistlayer comprises using a photo-curable photoresist film to form theplating resist layer, and exposing to light one surface of the annularportion on which a thirteenth mask and a light control sheet arestacked. The thirteenth mask behaves so as to inhibit light transmissionat front-surface pattern forming portions where either one of aconductor film of a front surface of the annular portion with theannular portion taken as an axis or a conductor film of a rear surfaceof the annular portion with the annular portion taken as an axis is tobe formed, to inhibit light transmission at side-portion pattern formingportions where conductor films of outer-and-inner side surfaces of theannular portion are to be formed with the annular portion taken as anaxis, and to permit light transmission at the other portions. The lightcontrol sheet behaves so as to make incident light scattered orrefracted and given off from a side opposite to the incident side. Theother surface of the annular portion on which a fourteenth mask and alight control sheet are stacked are also exposed to light. Thefourteenth mask behaves so as to inhibit light transmission atrear-surface pattern forming portions where either the other one of theconductor film of the front surface of the annular portion with theannular portion taken as an axis or the conductor film of the rearsurface of the annular portion with the annular portion taken as an axisis to be formed, to inhibit light transmission at a portion which is tobe laid on the annular hole or center hole, and to permit lighttransmission at the other portions, thus allowing only the exposedportions of the photoresist film to be cured. Thereafter, thephotoresist film is developed to thereby remove uncured portions otherthan the cured portions, so that the plating resist layer is formed ateach of portions other than the portions where the conductor film of thefront surface of the annular portion with the annular portion taken asan axis, the conductor film of the rear surface of the annular portionwith the annular portion taken as an axis, and the conductor films ofthe outer-and-inner side surfaces of the annular portion with theannular portion taken as an axis are to be formed.

According to a seventeenth aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to thethird aspect, wherein the process for patterning the plating resistlayer comprises using a photo-degradable photoresist film to form theplating resist layer, and exposing to light one surface of the annularportion on which a fifteenth mask and a light control sheet are stacked.The fifteenth mask behaves so as to permit light transmission atfront-surface pattern forming portions where either one of a conductorfilm of a front surface of the annular portion with the annular portiontaken as an axis or a conductor film of a rear surface of the annularportion with the annular portion taken as an axis is to be formed, topermit light transmission at side-portion pattern forming portions wherea conductor film of an outer side surface or inner side surface of theannular portion is to be formed with the annular portion taken as anaxis, and to inhibit light transmission at the other portions. The lightcontrol sheet behaving so as to make incident light scattered orrefracted and given off from a side opposite to the incident side. Theother surface of the annular portion on which a sixteenth mask and alight control sheet are stacked are also exposed to light. The sixteenthmask behaves so as to permit light transmission only at pattern formingportions where either the other one of the conductor film of the frontsurface of the annular portion with the annular portion taken as an axisor the conductor film of the rear surface of the annular portion withthe annular portion taken as an axis is to be formed, and to inhibitlight transmission at the other portions, thus allowing only the exposedportions of the photoresist film to be photo-degraded. Thereafter, thephotoresist film is developed to thereby remove only the photo-degradedportions, so that the plating resist layer is formed at each of portionsother than the portions where the conductor film of the front surface ofthe annular portion with the annular portion taken as an axis, theconductor film of the rear surface of the annular portion with theannular portion taken as an axis, and the conductor film of the outerside surface or inner side surface of the annular portion with theannular portion taken as an axis are to be formed.

According to an eighteenth aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to thefifth aspect, wherein the process for patterning the etching resistlayer comprises using a photo-curable photoresist film to form theetching resist layer, and exposing to light one surface of the annularportion on which a first mask and a light control sheet are stacked. Thefirst mask behaves so as to permit light transmission at front-surfacepattern forming portions where a conductor film of a front surface ofthe annular portion is to be formed with the annular portion taken as anaxis, to permit light transmission at side-portion pattern formingportions where a conductor film of an outer side surface or inner sidesurface of the annular portion is to be formed with the annular portiontaken as an axis, and to inhibit light transmission at the otherportions. The light control sheet behaves so as to make incident lightscattered or refracted and given off from a side opposite to theincident side. The other surface of the annular portion on which asecond mask and a light control sheet are stacked is also exposed tolight. The second mask behaves so as to permit light transmission atrear-surface pattern forming portions where a conductor film of a rearsurface of the annular portion is to be formed with the annular portiontaken as an axis, to permit light transmission at side-portion patternforming portions where a conductor film of an outer side surface orinner side surface of the annular portion is to be formed with theannular portion taken as an axis, and to inhibit light transmission atthe other portions. The light control sheet behaves so as to makeincident light scattered or refracted and given off from a side oppositeto the incident side, thus allowing only the exposed portions of thephotoresist film to be cured. Thereafter, the photoresist film isdeveloped to thereby remove uncured portions other than the curedportions, so that the etching resist layer is formed at each of portionswhere the conductor film of the front surface of the annular portionwith the annular portion taken as an axis, the conductor film of therear surface of the annular portion with the annular portion taken as anaxis, and the conductor film of the outer side surface or inner sidesurface of the annular portion with the annular portion taken as an axisare to be formed.

According to a nineteenth aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to thefifth aspect, wherein the process for patterning the etching resistlayer comprises using of a photo-degradable photoresist film to form theetching resist layer, and exposing to light one surface of the annularportion on which a third mask and a light control sheet are stacked. Thethird mask behaves so as to inhibit light transmission at front-surfacepattern forming portions where a conductor film of a front surface ofthe annular portion is to be formed with the annular portion taken as anaxis, to inhibit light transmission at side-portion pattern formingportions where a conductor film of an outer side surface or inner sidesurface of the annular portion is to be formed with the annular portiontaken as an axis, and to permit light transmission at the otherportions. The light control sheet behaves so as to make incident lightscattered or refracted and given off from a side opposite to theincident side. The other surface of the annular portion on which afourth mask and a light control sheet are stacked is also exposed tolight. The fourth mask behaves so as to inhibit light transmission atrear-surface pattern forming portions where a conductor film of a rearsurface of the annular portion is to be formed with the annular portiontaken as an axis, to inhibit light transmission at side-portion patternforming portions where a conductor film of an outer side surface orinner side surface of the annular portion is to be formed with theannular portion taken as an axis, and to permit light transmission atthe other portions. The light control sheet behaves so as to makeincident light scattered or refracted and given off from a side oppositeto the incident side, thus allowing only the exposed portions of thephotoresist film to be photo-degraded. Thereafter, the photoresist filmis developed to thereby remove only the photo-degraded portions, so thatthe etching resist layer is formed at each of portions where theconductor film of the front surface of the annular portion with theannular portion taken as an axis, the conductor film of the rear surfaceof the annular portion with the annular portion taken as an axis, andthe conductor film of the outer side surface or inner side surface ofthe annular portion with the annular portion taken as an axis are to beformed.

According to a twentieth aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to thefifth aspect, wherein the process for patterning the etching resistlayer comprises using, a photo-curable photoresist film to form theetching resist layer, and exposing to light one surface of the annularportion on which a fifth mask and a light control sheet are stacked. Thefifth mask behaves so as to permit light transmission at front-surfacepattern forming portions where either one of a conductor film of a frontsurface of the annular portion with the annular portion taken as an axisor a conductor film of a rear surface of the annular portion with theannular portion taken as an axis is to be formed, to permit lighttransmission at side-portion pattern forming portions where a conductorfilm of an outer side surface or inner side surface of the annularportion is to be formed with the annular portion taken as an axis, andto inhibit light transmission at the other portions. The light controlsheet behaves so as to make incident light scattered or refracted andgiven off from a side opposite to the incident side. The other surfaceof the annular portion on which a sixth mask is stacked is also exposedto light. The sixth mask behaves so as to permit light transmission atrear-surface pattern forming portions where either the other one of theconductor film of the front surface of the annular portion with theannular portion taken as an axis or the conductor film of the rearsurface of the annular portion with the annular portion taken as an axisis to be formed, and to inhibit light transmission at the otherportions, thus allowing only the exposed portions of the photoresistfilm to be cured. Thereafter, the photoresist film is developed tothereby remove uncured portions other than the cured portions, so thatthe etching resist layer is formed at each of portions where theconductor film of the front surface of the annular portion with theannular portion taken as an axis, the conductor film of the rear surfaceof the annular portion with the annular portion taken as an axis, andthe conductor film of the outer side surface or inner side surface ofthe annular portion with the annular portion taken as an axis are to beformed.

According to a twenty-first aspect of the present invention, there isprovided the toroidal printed coil manufacturing method according to thefifth aspect, wherein the process for patterning the etching resistlayer comprises using a photo-degradable photoresist film to form theetching resist layer, and exposing to light one surface of the annularportion on which a seventh mask and a light control sheet are stacked.The seventh mask behaves so as to inhibit light transmission atfront-surface pattern forming portions where either one of a conductorfilm of a front surface of the annular portion with the annular portiontaken as an axis or a conductor film of a rear surface of the annularportion with the annular portion taken as an axis is to be formed, toinhibit light transmission at side-portion pattern forming portionswhere a conductor film of an outer side surface or inner side surface ofthe annular portion is to be formed with the annular portion taken as anaxis, and to permit light transmission at the other portions. The lightcontrol sheet behaves so as to make incident light scattered orrefracted and given off from a side opposite to the incident side. Theother surface of the annular portion on which an eighth masks stacked isalso exposed to light. The eighth mask behaves so as to inhibit lighttransmission at lead pattern forming portions where either the other oneof the conductor film of the front surface of the annular portion withthe annular portion taken as an axis or the conductor film of the rearsurface of the annular portion with the annular portion taken as an axisis to be formed, to inhibit light transmission at a portion which is tobe laid on a through hole, and to permit light transmission at the otherportions, thus allowing only the exposed portions of the photoresistfile to be photo-degraded. Thereafter, the photoresist film is developedto thereby remove only the photo-degraded portions, so that the etchingresist layer is formed at each of portions where the conductor film ofthe front surface of the annular portion with the annular portion takenas an axis, the conductor film of the rear surface of the annularportion with the annular portion taken as an axis, and the conductorfilm of the outer side surface or inner side surface of the annularportion with the annular portion taken as an axis are to be formed.

BRIEF DESCRIPTION OF DRAWINGS

These and other aspects and features of the present invention willbecome clear from the following description taken in conjunction withthe preferred embodiments thereof with reference to the accompanyingdrawings, in which:

FIG. 1 is a partial perspective view showing a printed coil sheet usedfor the toroidal printed coil manufacturing method according to a firstembodiment of the present invention;

FIG. 2 is a partial perspective view showing a printed coil sheet usedfor the toroidal printed coil as well as its manufacturing method of thefirst embodiment of the present invention;

FIG. 3 is a perspective view of a toroidal printed coil cut out from theprinted coil sheet shown in FIG. 1;

FIG. 4 is a perspective view of a toroidal printed coil cut out from theprinted coil sheet shown in FIG. 2;

FIG. 5 is a perspective view of a toroidal printed coil manufactured bya toroidal printed coil and its manufacturing method of anotherembodiment of the present invention;

FIG. 6 is a perspective view of a toroidal printed coil manufactured bya toroidal printed coil and its manufacturing method of still anotherembodiment of the present invention;

FIG. 7 is an explanatory view for explaining a state in which theconductor film is formed into a spiral shape;

FIG. 8 is an explanatory view showing a printed coil manufacturingmethod according to the prior art;

FIG. 9 is an explanatory view showing a process in which part of thephotoresist film for the conductor film of the outer side surface orinner side surface of the side wall surface of the annular hole orcenter hole according to a toroidal printed coil of another embodimentof the present invention is exposed to light;

FIG. 10 is an explanatory view showing a process in which part of thephotoresist film for the conductor film of the outer side surface orinner side surface of the side wall surface of the annular hole orcenter hole according to a toroidal printed coil of a modification ofanother embodiment of the present invention is exposed to light;

FIG. 11 is an explanatory view showing a process in which part of thephotoresist film for the conductor film of the outer side surface orinner side surface of the side wall surface of the annular hole orcenter hole according to a toroidal printed coil of still anothermodification of another embodiment of the present invention is exposedto light;

FIG. 12 is an explanatory view showing a process in which part of thephotoresist film for the conductor film of the outer side surface orinner side surface of the side wall surface of the annular hole orcenter hole according to a toroidal printed coil of yet anothermodification of another embodiment of the present invention is exposedto light;

FIG. 13 is a sectional view showing a process in which part of thephotoresist film is exposed to light;

FIG. 14 is a sectional view showing a process in which part of thephotoresist film is exposed to light;

FIG. 15 is a sectional view showing a process in which part of thephotoresist film is exposed to light;

FIGS. 16 is a sectional view showing a process in which part of thephotoresist film is exposed to light;

FIG. 17 is a sectional view showing a process in which part of thephotoresist film is exposed to light; and

FIG. 18 is a sectional view showing a process in which part of thephotoresist film is exposed to light.

DETAILED DESCRIPTION OF THE INVENTION

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numeralsthroughout the accompanying drawings.

Now a first embodiment of the present invention is described in detailwith reference to the accompanying drawings.

A toroidal printed coil and its manufacturing method according to anembodiment of the present invention, as well as a toroidal printed coilmanufactured by the manufacturing method are described below in detailwith reference to the accompanying drawings.

FIGS. 1 and 2 are partial perspective views of printed coil sheets 70 tobe used for toroidal printed coil manufacturing methods according to thefirst embodiment and a second embodiment of the present invention,respectively. FIGS. 3 and 4 are perspective views of toroidal printedcoils P cut out from the printed coil sheets 70 used for the toroidalprinted coil manufacturing methods of the first embodiment and thesecond embodiment shown in FIG. 1 and FIG. 2, respectively.

In the figures, reference numeral 1 denotes an insulating substrate, 2denotes a generally C-shaped annular hole formed through the insulatingsubstrate 1, 3 denotes a circular (FIG. 1) or hexagonal (FIG. 2) centerhole formed through the insulating substrate 1, 4 denotes an annular jutformed by the annular hole 2 and the center hole 3, 5 denotes an annularportion of the annular jut 4, 6 denotes a conductor film formed spirallyat front-and-rear surfaces and inner-and-outer side surfaces of theannular portion 5, 7 denotes a connecting portion for connecting theannular portion 5 of the annular jut 4 and the portion (i.e., baseportion) other than the annular jut 4 to each other, 8 denotes twoterminals of the conductor film 6 formed in the annular portion 5 nearthe connecting portion 7, and P denotes a toroidal printed coil. Thefirst embodiment and the second embodiment have the same basicconstruction, only differing from each other in the configurations ofthe annular hole 2, the center hole 3, and the annular portion 5, andtherefore are described in combination.

For the toroidal printed coil manufacturing methods of the first andsecond embodiments of FIGS. 1 and 2, the printed coil sheet 70 is formedso that a plurality of annular holes 2 and a plurality of center holes 3surrounded by these annular holes 2 are provided in and through theinsulating substrate 1, and each annular jut 4 is defined by an annularhole 2 and a center hole 3 placed inside the annular hole 2 with aspecified spacing. Then, in this printed coil sheet 70, with the annularportion 5 of each annular jut 4 taken as an axis, the strip-shapedconductor film 6 is formed continuously in a spiral shape atfront-and-rear surfaces and inner-and-outer side surfaces of the annularportion 5 so as to be wrapped helically around annular portion 5 withrespect to the annular axis of the annular portion 5 as shown in FIG. 7,by which a plurality of toroidal printed coils P are formedsimultaneously. That is, referring to FIG. 7, a conductor film 6 a ofthe front surface of the annular portion 5 is formed so as to beconnected to a conductor film 6 b of the outer side surface of theannular portion 5, a conductor film 6 c of the rear surface of theannular portion 5, and a conductor film 6 d of the inner side surface ofthe annular portion 5, continuously in this order, where the conductorfilm 6 d of the inner side surface of the annular portion 5 is connectedto a conductor film 6 a adjacent to the foregoing conductor film 6 a ofthe front surface of the annular portion 5. As a result of this, thecontinuous conductor film strip 6 is formed spirally around the annularportion 5.

As the insulating substrate 1, those sheets having insulative propertyat the front-and-rear surfaces and all the side surfaces are usable,exemplified by laminated sheets of paper base phenolic resin, paper baseepoxy resin, synthetic-fiber-fabric base epoxy resin, glass-cloth papercomposite epoxy resin, glass-cloth and glass-nonwoven-fabric compositeepoxy resin, glass-cloth base epoxy resin, and glass-cloth base Teflonresin; or resins such as polyetherimide resin, polysulfone resin,polyether sulfone resin, benzocyclobutene resin, and Teflon resin; orceramics such as aluminum nitride, silicon carbide, and alumina. Inaddition, the form of the insulating substrate 1 may be plate-shaped,sheet-shaped, or film-shaped.

Each of the annular juts 4 comprises an annular portion 5, which is anannular portion sandwiched between one annular hole 2 and one centerhole 3 surrounded by this annular hole 2, and a connecting portion 7 forconnecting the annular portion 5 and the base portion 71 of the printedcoil sheet 70 to each other. As each annular jut 4 of the printed coilsheet 70 in the first embodiment of FIG. 1, the center hole 3 iscircular shaped and the perimeter profile of the annular jut 4 has acircular shape concentric with the circular shape of the center hole 3(see FIG. 1). Also, as each annular jut 4 of the printed coil sheet 70in the second embodiment of FIG. 2, the center hole 3 is polygonalshaped, for example, hexagonal shaped, and the perimeter profile of theannular jut 4 has a polygonal shape, e.g. hexagonal shape, correspondingto the polygonal shape of the center hole 3 (see FIG. 2).

As another example of the annular jut 4, it is also possible that, asshown in FIG. 6, a center hole 43 is circular shaped and the perimeterprofile of an annular portion 45 of the annular jut 4 is polygonalshaped.

As yet another example of the annular jut 4, it is also possible that,as shown in FIG. 5, a center hole 53 is polygonal shaped, e.g. hexagonalshaped, and the perimeter profile of an annular portion 55 of theannular jut 4 is circular shaped.

As still another example of the annular jut 4, it is also possible thatthe center hole 3 is elliptical shaped and the perimeter of the annularjut 4 has an elliptical shape similar to the center hole.

The sizes and shapes of the annular hole 2 and the center hole 3 as wellas of the annular jut 4 formed by these are not particularly limited andmay be selected as appropriate depending on applications. The shape ofthe annular jut 4 may be generally C-shaped or D-shaped as an example.

Usable processes for forming the annular hole 2 and the center hole 3are, for example, press working, router working, laser processing, NCdrilling or the like.

The conductor film 6 can be formed by various methods. As an example ofthe methods, in the front-and-rear surfaces and inner-and-outer sidesurfaces of the annular jut 4, a plating resist layer is formed atportions except for portions of those surfaces to be left as theconductor film 6, and then those surfaces are plated so that theconductor film 6 is formed at the portions to be left as the conductorfilm 6. As another example, there is a method which includes forming aconductor film generally entirely at the front-and-rear surfaces andinner-and-outer side surfaces of the annular jut 4. Then, unnecessaryportions of the generally entirely formed conductor film are removed byirradiation of a laser beam or the like so that the conductor film 6 isformed only at necessary portions, or by forming an etching resist layerat portions to be left as the conductor film 6 out of the generallyentirely formed conductor film and further performing an etching processto thereby remove unnecessary portions out of the generally entirelyformed conductor film so that the conductor film 6 is formed only atnecessary portions, thus the conductor film 6 being formed. Portionswhere the conductor film 6 is formed may be either the entirety or partof the perimeter of the annular jut 4.

Next, the method of patterning the conductor film 6 is explained indetail with reference to FIGS. 9 to 18. It is noted that the referencenumerals used in the first and second embodiments are used also for thefollowing description as a typical example. Further, although onlyeither one of the first embodiment or the second embodiment is shown insome figures for simplification of the figures, it is needless todaythat those figures are also applicable to the other embodiments that arenot shown.

Here are described four types of methods concretely.

First of all, a first method is a method in which, as shown in FIGS. 13and 15, an insulating substrate 38 (which will be the insulatingsubstrate 1 after completion) coated with a photoresist film is exposedto light one-by-one in an order of FIG. 13 and FIG. 15 or in its reverseorder, where a light control sheet 34 is used for only one surface ofthe insulating substrate 38. In addition, a modification in which a mask33 and the light control sheet 34 may be in a positional relationreverse to that of FIG. 13 with respect to the insulating substrate 38is shown in FIG. 14.

In a second method, as shown in FIGS. 13 and 16, an insulating substrate38 coated with a photoresist film is exposed to light one-by-one in anorder of FIG. 13 and FIG. 16, or in its reverse order, and the lightcontrol sheet 34 is used for both surfaces of the insulating substrate38.

In a third method, as shown in FIG. 17, an insulating substrate 38coated with a photoresist film is exposed to light simultaneously atboth surfaces, and the light control sheet 34 is used on only onesurface of the insulating substrate 38.

In a fourth method, as shown in FIG. 18, an insulating substrate 38coated with a photoresist film is exposed to light at both surfaces, andthe light control sheets 34 are used on both surfaces of the insulatingsubstrate 38.

More specifically, in the first method, a photoresist film 32 forforming the etching resist layer and the plating resist layer,respectively, is exposed to light in the following manner.

First, the mask 33 and the light control sheet 34 are laid on onesurface, e.g. the top surface of FIG. 11, of the insulating substrate38, and then, as shown in FIG. 13, light is transmitted through thelight control sheet 34 and light transmitting parts 35 of the mask 33 sothat the photoresist film 32 is exposed to light from above downward.This mask 33 and each of masks 33 described below may be made from aglass or acrylic film sheet or the like.

Subsequently, another mask 33 is laid on the other surface, e.g. thebottom surface of FIG. 11, of the insulating substrate 38, and then, asshown in FIG. 15, light is transmitted through the light transmittingparts 35 of the mask 33 so that the photoresist film 32 is exposed tolight from below upward. After that, the photoresist film 32 isdeveloped, by which an etching resist layer or a plating resist layerhaving a pattern corresponding to the pattern of the mask 33 is formed.

In this first method, for the formation of the etching resist by using aphoto-curable material as the photoresist film 32, as shown in FIG. 11,in the front-surface side mask 33 (upper-side mask in FIG. 11) to belocated on the front surface side of the insulating substrate 1 out oftwo masks 33, front-surface pattern forming portions 33 a formed into apattern corresponding to a conductor film 6 (specifically a portion offilm 6 corresponding to the portion 6 a of FIG. 7) of the front surfaceof the annular portion 5 with the annular portion 5 taken as an axis,and side-portion pattern forming portions 33 b which are formed into apattern corresponding to a conductor film 6 (specifically, correspondingto the portion 6 b of FIG. 7) of the outer side surface or a conductorfilm 6 (specifically corresponding to the portion 6 d of FIG. 7) of theinner side surface of the annular portion 5 to be connected to theconductor film 6 a of the front surface of the annular portion 5 withthe annular portion 5 taken as an axis and which are connected to thefront-surface pattern forming portions 33 a these portions of the mask33 are formed so as to be the transparent light transmitting parts 35,respectively, and the other portions are formed opaque as opticalshielding parts. Therefore, the portions corresponding to thefront-surface pattern forming portions 33 a and the side-portion patternforming portions 33 b are the light transmitting parts 35 and transmitlight, so that portions of the photoresist film 32 corresponding to thefront-surface pattern forming portions 33 a and the side-portion patternforming portions 33 b are exposed to light and thereby cured. The otherportions do not transmit light and so are not exposed to light and arenot cured. On the other hand, in the rear-surface side mask 33(lower-side mask 33 in FIG. 11) to be located on the rear surface sideof the insulating substrate 1, only rear-surface pattern formingportions 33 c formed into a pattern in correspondence to the conductorfilm 6 (specifically corresponding to the portion 6 c of FIG. 7) of therear surface of the annular portion 5 with the annular portion 5 takenas an axis are formed so as to be the transparent light transmittingpart 35, where the other portions are formed opaque as optical shieldingpart. Therefore, the portions corresponding to the rear-surface patternforming portions 33 c are the light transmitting parts 35 and sotransmit light, so that portions of the photoresist film 32corresponding to the rear-surface pattern forming portions 33 c and theside-portion pattern forming portions 33 d are exposed to light and arethereby cured. The other portions, however, do not transmit light and soare not exposed to light and not cured. As a result, in the developingprocess after exposure, the uncured portions are removed by a developerwhile the cured portions are left unremoved thereby, so that an etchingresist layer is formed at portions corresponding to the conductor films6 a, 6 c, 6 b, 6 d of the front-and-rear surfaces and inner-and-outerside surfaces of the annular portion 5 with the annular portion 5 takenas an axis. It is noted that dotted line 33 e on each mask 33 in FIG. 11represents the position where the mask is laid on the annular hole 2 orcenter hole 3. Also, as will be detailed later, the light control sheet34 scatters or refracts incident light, then gives off the light from aside opposite to the incident side, so that the photoresist film 32 ofthe side wall surface where the conductor film 6 b or 6 d of the outerside portion or inner side portion of the annular portion 5 within theannular hole 2 or center hole 3 is to be formed is irradiated with thelight.

Also in the first method, for the formation of etching resist by using aphoto-degradable material as the photoresist film 32, as shown in FIG.12, in the front-surface side mask 33 (upper-side mask in FIG. 12) to belocated on the front surface side of the insulating substrate 1 out oftwo masks 33, front-surface pattern shielding portions 33 f which areformed into a pattern corresponding to the conductor film 6 a of thefront surface of the annular portion 5 with the annular portion 5 takenas an axis, and side-portion pattern shielding portions 33 g which areformed into a pattern corresponding to the conductor film 6 of the outerside surface or the conductor film 6 of the inner-side-surface of theannular portion 5 connected to the conductor film 6 a of the frontsurface of the annular portion 5 with the annular portion 5 taken as anaxis and which are connected to the front-surface pattern shieldingportions 33 f are formed so as to be opaque as optical shielding parts135, respectively, where the other portions are formed as transparentlight transmitting parts 35. Therefore, the portions corresponding tothe front-surface pattern shielding portions 33 f and the side-portionpattern shielding portions 33 g are the optical shielding parts 135 andso do not transmit light, so that portions of the photoresist film 32corresponding to the front-surface pattern shielding portions 33 f andthe side-portion pattern shielding portions 33 g are not exposed tolight and so not degraded, while the other portions transmit light andso are degraded. On the other hand, in the rear-surface side mask 33(lower-side mask 33 in FIG. 12) to be located on the rear surface sideof the insulating substrate 1, rear-surface pattern shielding portions33 h formed into a pattern corresponding to the conductor film 6 of therear surface of the annular portion 5 with the annular portion 5 takenas an axis, and a portion 33 e to be laid on the annular hole 2 orcenter hole 3, are formed so as to be opaque as optical shielding parts135, respectively. However, the other portions are formed as transparentlight transmitting parts 35. Therefore, the rear-surface patternshielding portions 33 h and the portion corresponding to the portion 33e that is to be laid on the annular hole 2 or center hole 3 are theoptical shielding parts 135 and so do not transmit light, so thatportions of the photoresist film 32 corresponding to the rear-surfacepattern shielding portions 33 h are not exposed to light and so notdegraded. Moreover, a wall portion corresponding to the conductor film 6b or 6 d of the outer side portion or inner side portion of the annularportion 5 within the annular hole 2 or center hole of the photoresistfilm 32 is not exposed to light so that the portions corresponding tothe side-portion pattern shielding portions 33 g are not degraded, whilethe other portions transmit light and so are degraded. As a result, inthe developing process after the exposure, the degraded portions areremoved by the developer while the undegraded portions are not removedby the developer and left, so that etching resist layers are formed atportions corresponding to the conductor films 6 a, 6 c, 6 b, 6 d of thefront-and-rear surfaces and inner-and-outer side surfaces of the annularportion 5 with the annular portion 5 taken as an axis. It is noted thatdotted line 33 e on each mask 33 in FIG. 12 represents the positionwhere the mask is laid on the annular hole 2 or center hole 3.

Next, the second method is substantially the same as the above-describedfirst method except that when another mask 33 is laid on the othersurface of the insulating substrate 38, the light control sheet 34 isalso laid thereon as shown in FIG. 16, in which state the light controlsheet 34 and the light transmitting part 35 of the mask 33 transmitlight so that the photoresist film 32 is exposed to light from belowupward, and except that the lower-side mask pattern is different fromthat of the first embodiment (see FIGS. 9 and 10).

In the case where the photoresist film 32 is a photo-curable type offilm, in the rear-surface side mask 33 (the lower-side mask 33 in FIG.9) to be located on the rear surface side of the insulating substrate 1,the rear-surface pattern forming portions 33 c formed into a patterncorresponding to the conductor film 6 of the rear surface of the annularportion 5 with the annular portion 5 taken as an axis, and theside-portion pattern forming portions 33 d which are formed into apattern corresponding to the connecting portion 7 to be connected to theconductor film 6 of the rear surface of the annular portion 5 with theannular portion 5 taken as an axis and which are connected to therear-surface pattern forming portions 33 c, are formed so as to betransparent light transmitting parts 35, respectively, while the otherportions are formed as opaque optical shielding parts. Therefore, theportions corresponding to the rear-surface pattern forming portions 33 cand the side-portion pattern forming portions 33 d are the lighttransmitting parts 35 and so transmit light, so that the portions of thephotoresist film 32 corresponding to the rear-surface pattern formingportions 33 c and the side-portion pattern forming portions 33 d areexposed to light and thereby cured, while the other portions do nottransmit light and so are not cured. Also, in the case where thephotoresist film 32 is a photo-degradable type, in the rear-surface sidemask 33 (the lower-side mask 33 in FIG. 10) to be located on the rearsurface side of the insulating substrate 1, the rear-surface patternforming portions 33 c formed into a pattern with the annular portion 5taken as an axis and corresponding to the conductor film 6 of the rearsurface of the annular portion 5, and the side-portion pattern formingportions 33 d which are formed into a pattern with the annular portion 5taken as an axis and corresponding to the connecting portion 7 connectedto the conductor film 6 of the rear surface of the annular portion 5 andwhich are connected to the rear-surface pattern forming portions 33 c,are formed opaque as the optical shielding parts 135, respectively,while the other portions are formed transparent as light transmittingparts. Therefore, the portions corresponding to the rear-surface patternforming portions 33 c and the side-portion pattern forming portions 33 dare the optical shielding parts and do not transmit light, so that theportions corresponding to the rear-surface pattern forming portions 33 cand the side-portion pattern forming portions 33 d of the photoresistfilm 32 formed corresponding to the front-and-rear surfaces andinner-and-outer side surfaces of the annular portion 5 with the annularportion 5 taken as an axis are exposed to light and thereby cured, whilethe other portions are not exposed to light and so not cured. Also, inthe case where the photoresist film 32 is a photo-degradable type, inthe rear-surface side mask 33 (the lower-side mask 33 in FIG. 10) to belocated on the rear surface side of the insulating substrate 1, therear-surface pattern forming portions 33 c formed into a patterncorresponding to the conductor film 6 of the rear surface of the annularportion 5 with the annular portion 5 taken as an axis, and theside-portion pattern forming portions 33 d which are formed into apattern corresponding to the connecting portion 7 to be connected to theconductor film 6 of the rear surface of the annular portion 5 with theannular portion 5 taken as an axis and which are connected to therear-surface pattern forming portions 33 c, are formed as the opaqueoptical shielding parts 135, respectively, while the other portions areformed as transparent light transmitting parts. Therefore, the portionscorresponding to the rear-surface pattern forming portions 33 c and theside-portion pattern forming portions 33 d are the optical shieldingparts and so do not transmit light. Therefore, portions other than theportions corresponding to the rear-surface pattern forming portions 33 cand the side-portion pattern forming portions 33 d of the photoresistfilm 32 formed at the front-and-rear surfaces and inner-and-outer sidesurfaces of the annular portion 5 with the annular portion 5 taken as anaxis are exposed to light and thereby degraded, while the portionscorresponding to the rear-surface pattern forming portions 33 c and theside-portion pattern forming portions 33 d are not exposed to light andare not degraded.

Next, the third method is that the steps of FIG. 13 and FIG. 15 in thefirst method are carried out simultaneously as shown in FIG. 17. Also,the fourth method is that the steps of FIG. 13 and FIG. 16 in the secondmethod are carried out simultaneously as shown in FIG. 18.

In addition, the insulating substrates 38 coated with the photoresistfilms 32 are shown in FIGS. 9 to 12 of the first to fourth methods.However, in the case where an etching resist layer is formed, a metallayer is present between the photoresist film 32 and the insulatingsubstrate 38 as a matter of course. Also, in the case where a platingresist layer is formed in the first to fourth methods, the masks are setwith such a change that the resist layer is formed by exposure anddevelopment processes at the portions other than the conductor films 6a, 6 c, 6 b, 6 d of the front-and-rear surfaces and inner-and-outer sidesurfaces of the annular portion 5 with the annular portion 5 taken as anaxis.

In the first to fourth methods, the light control sheet 34 exertscontrol so that collimated light 36 from a light source is changed intoscattered light or refracted light 37 and so that part of the resultinglight is directed to the side wall surface of the conductor film 6 b or6 d of the outer side portion or inner side portion of the annularportion 5 within the annular hole 2 or center hole 3 (see FIG. 13). Asthe light control sheet 34, for example, sheets having minute pits andprojections provided on the surface like a diffusion sheet or havingfine particles or air bubbles contained inside, and sheets havingprismatic projections on the surface like a prism sheet are usable.Without the light control sheet 34, it would be difficult to apply thelight that has been transmitted through the light transmitting part 35of the mask 33 to the side wall surfaces of the annular hole 2 and thecenter hole 3, so that the patterned etching resist layer or platingresist layer of the conductor film 6 b or 6 d of the outer side portionor inner side portion of the annular portion 5 could not be formed atthe side wall surface within the annular hole 2 or center hole 3. Thatis, by exposure via the light control sheet 34 and the masks 33, theetching resist layer or the plating resist layer can be formedsimultaneously at the conductor films 6 a, 6 c, 6 b, 6 d of thefront-and-rear surfaces and inner-and-outer side surfaces of the annularportion 5 with the annular portion 5 taken as an axis. Thus, a processcut can be realized.

Here is discussed a comparison between a case where a prisim sheet isused as the light control sheet 34 and another case where a diffusionsheet is used therefor. The prism sheet (bidirectional refractive sheet)has such a configuration that the quantity of light directed in two waysis larger than that of the diffusion sheet. Conversely, in the diffusionsheet, because light is also directed in ways other than the two ways,the quantity of light directed in two ways is smaller than the quantityof light directed by the prism sheet by the degree, resulting in lessexposure. Therefore, it is preferable to use a prism sheet rather than adiffusion sheet because a relatively sharper image can be formed, when aconductor film of the outer side portion or a conductor film of theinner side portion is formed at an end face in the light-travelingdirection, i.e., at the side wall surface of the annular hole 2 orcenter hole 3 of the substrate sheet.

The order in which the mask 33 and the light control sheet 34 arearranged for stacking may be that the light control sheet 34 ispositioned lower (see FIG. 14). Light used for the exposure is given bya light source such as solar light, mercury lamp, xenon lamp, arc light,argon laser or the like. In addition, the exposure of one surface of thesubstrate 38 and the exposure of the other surface may be performedeither simultaneously or sequentially one-by-one. Whereas FIGS. 13 and14 show an example where an etching resist layer is formed, theconductor film 6 is omitted in the case where a plating resist layer isformed.

In the development process, in the case where the photoresist film 32 isa photo-curable type, the process is carried out by using sodiumcarbonate as the developer and by selectively removing uncured portionsof the photoresist film 32. When the photoresist film 32 is aphoto-degradable type, the developing process is carried out by usingmetasilicate sodium or the like as the developer and by selectivelyremoving photo-degraded portions of the photoresist film 32.

As the method for forming the pattern of the conductor film 6 of theouter side surface or the conductor film 6 of the inner side surface ofthe annular portion 5 within the annular hole 2 and the center hole 3,the method using an etching resist layer or a plating resist layer asdescribed above is most preferable, but the conductor film 6 may be cutaway by laser or other physical means.

It is also possible that the conductor film 6 a of the front surface ofthe annular portion 5 with the annular portion 5 taken as an axis, orthe conductor film 6 a of the rear surface of the annular portion 5 withthe annular portion 5 taken as an axis is partly insulated with solderresist. The material of the solder resist may be epoxy resin, varnish,enamel or the like. The method for forming the solder resist may bescreen printing, roll coater, curtain coater, spraying, or electrostaticcoating or the like.

It is also possible that the conductor film 6 a of the front surface ofthe annular portion 5 with the annular portion 5 taken as an axis, orthe conductor film 6 a of the rear surface of the annular portion 5 withthe annular portion 5 taken as an axis is partly or entirelysurface-treated. The surface treatment may be implemented by solderleveler, gold plating, solder plating, nickel plating, silver plating,palladium plating or the like. The surface-treated layer formed by thesesurface treatments may be provided either as a plurality of layers inappropriate combinations, or as a single layer. As an exception, agold-plated single layer alone will not do, and normally a gold-platedlayer is stacked on a nickel-plated layer. Further, for plated layers ofsurface treatment, electroless plating is applicable when the conductorfilm is formed inside the annular hole 2 and the center hole 3.

In addition, in the masks 33, the front-surface pattern forming portions33 a are formed into a pattern corresponding to the conductor film 6 aof the front surface of the annular portion 5 with the annular portion 5taken as an axis. The side-portion pattern forming portions 33 b areformed into a pattern corresponding to the conductor film 6 of the outerside surface or the conductor film 6 of the inner side surface of theannular portion 5 to be connected to the conductor film 6 a of the frontsurface of the annular portion 5 with the annular portion 5 taken as anaxis, and the side-portion pattern forming portions 33 b are connectedto the front-surface pattern forming portions 33 a. The rear-surfacepattern forming portions 33 c are formed into a pattern corresponding tothe conductor film 6 of the rear surface of the annular portion 5 withthe annular portion 5 taken as an axis. The side-portion pattern formingportions 33 d are formed into a pattern corresponding to the conductorfilm 6 of the outer side surface or the conductor film 6 of the innerside surface of the annular portion 5 to be connected to the conductorfilm 6 of the rear surface of the annular portion 5 with the annularportion 5 taken as an axis, and the side-portion pattern formingportions 33 d are connected to the rear-surface pattern forming portions33 c. Howvever, the invention is not limited to this arrangement. Thatis, with the two masks 33 reversed in positional relation withrespect-to the substrate 38, the front-surface pattern forming portions33 a may be formed into a pattern corresponding to the conductor film 6of the rear surface of the annular portion 5 with the annular portion 5taken as an axis. The side-portion pattern forming portions 33 b arethen formed into a pattern corresponding to the conductor film 6 of theouter side surface or the conductor film 6 of the inner side surface ofthe annular portion 5 to be connected to the conductor film 6 of therear surface of the annular portion 5 with the annular portion 5 takenas an axis, and the side-portion pattern forming portions 33 b areconnected to the front-surface pattern forming portions 33 a. Therear-surface pattern forming portions 33 c are formed into a patterncorresponding to the conductor film 6 a of the front surface of theannular portion 5 with the annular portion 5 taken as an axis. Theside-portion pattern forming portions 33 d are formed into a patterncorresponding to the conductor film 6 of the outer side surface or theconductor film 6 of the inner side surface of the annular portion 5 tobe connected to the conductor film 6 a of the front surface of theannular portion 5 with the annular portion 5 taken as an axis, and theside-portion pattern forming portions 33 d are connected to therear-surface pattern forming portions 33 c.

Similarly, the front-surface pattern shielding portions 33 f are formedinto a pattern corresponding to the conductor film 6 a of the frontsurface of the annular portion 5 with the annular portion 5 taken as anaxis. The side-portion pattern shielding portions 33 g are formed into apattern corresponding to the conductor film 6 of the outer side surfaceor the conductor film 6 of the inner side surface of the annular portion5 to be connected to the conductor film 6 a of the front surface of theannular portion 5 with the annular portion 5 taken as an axis, and theside-portion pattern shielding portions 33 g are connected to thefront-surface pattern shielding portions 33 f The rear-surface patternshielding portions 33 h are formed into a pattern corresponding to theconductor film 6 of the rear surface of the annular portion 5 with theannular portion 5 taken as an axis. However, this invention is notlimited to this arrangement. That is, with the two masks 33 reversed inpositional relation with respect to the substrate 38, the front-surfacepattern shielding portions 33 f may be formed into a patterncorresponding to the conductor film 6 of the rear surface of the annularportion 5 with the annular portion 5 taken as an axis. The side-portionpattern shielding portions 33 g are then formed into a patterncorresponding to the connecting portion 7 to be connected to theconductor film 6 of the rear surface of the annular portion 5 with theannular portion 5 taken as an axis, and the side-portion patternshielding portions 33 g are connected to the front-surface patternshielding portions 33 f. The rear-surface pattern shielding portions 33h are formed into a pattern corresponding to the conductor film 6 a ofthe front surface of the annular portion 5 with the annular portion 5taken as an axis. Except for cases where the cutting is done by laser orother physical means, by these methods using exposure as describedabove, it becomes possible to expose to light, either by sequentialsteps or simultaneously, the conductor film 6 a of the front surface ofthe annular portion 5 as well as the conductor film 6 of the outer sidesurface or the conductor film 6 of the inner side surface of the annularportion 5 with the annular portion 5 taken as an axis, and the conductorfilm 6 of the rear surface of the annular portion 5 with the annularportion 5 taken as an axis. In addition, by a one-time developing step,etching resist or plating resist for the conductor film 6 a is formed onthe front surface of the annular portion 5 as well as the conductor film6 of the outer side surface or the conductor film 6 of the inner sidesurface of the annular portion 5 with the annular portion 5 taken as anaxis, and for the conductor film 6 of the rear surface of the annularportion 5 with the annular portion 5 taken as an axis. Therefore, theconductor film 6 a of the front surface of the annular portion 5 as wellas the conductor film 6 of the outer side surface or the conductor film6 of the inner side surface of the annular portion 5 with the annularportion 5 taken as an axis, and the conductor film 6 of the rear surfaceof the annular portion 5 with the annular portion 5 taken as an axis canbe formed at the front-and-rear surfaces and inner-and-outer sidesurfaces of the annular portion 5 with the annular portion 5 taken as anaxis, simultaneously by etching or plating, with high efficiency andwith low price.

The material for forming the conductor film 6 may be any one which haselectrical conductivity, exemplified by Such metals as copper, nickel,and gold.

The width of the conductor film 6 is not particularly limited, andnormally about 0.05 mm-1 mm widths suffice. The width of the conductorfilm 6 may be entirely uniform of course, but also may be nonuniform.For example, with an arrangement in which the width of the conductorfilm 6 gradually increases along the turning direction, a widerbandwidth of frequency can be obtained.

The thickness of the conductor film 6 is also not particularly limited,and normally 3 μm-50 μm thicknesses suffice.

The number of turns of the conductor film 6 (i.e., the number of turnsof the coil) is selected depending on the use of the printed coil.

In addition, surface treatment may be performed on part or all of theconductor film 6. The surface treatment in this case may be implementedby solder leveler, gold plating, solder plating, nickel plating or thelike.

Further, the conductor film 6 of portions other than the portions thatform the two terminals 8 of the toroidal printed coil P may be insulatedwith solder resist. The material of the solder resist may be epoxyresin, varnish, enamel or the like. The method for forming the solderresist may be a screen printing process, roll coater process, curtaincoater process, spraying process, electrostatic coating process or thelike.

In the toroidal printed coil manufacturing methods according to thefirst and second embodiments of the present invention, each toroidalprinted coil P can be obtained only by cutting each annular jut 4 of theprinted coil sheet 70 at the connecting portion 7 out of the insulatingsubstrate 1. The cutting place for obtaining the toroidal printed coilP, without any particular limitations, may be such that the connectingportion 7 is either separated away on the toroidal printed coil P sideby cutting at the boundary portion between the connecting portion 7 andthe base portion 71 of the printed coil sheet 70 (see FIG. 3), or leftremaining on the base portion 71 side of the printed coil sheet 70 bycutting at the boundary portion between the connecting portion 7 and theannular portion 5 (see FIG. 4).

The toroidal printed coil P cutting method for obtaining individualtoroidal printed coils P from the printed coil sheet 70 may be punchingpress working, router working, laser cutting process, V cutting process,sheet cutting process or the like.

As shown above, in the toroidal printed coil manufacturing methods ofthe first and second embodiments of the present invention, the printedcoil sheet 70 in which toroidal printed coils P have been formed may beused, as it is, as a printed wiring board having toroidal printed coilsP. Alternatively, other circuits may be formed in the toroidal printedcoils P cut at the connecting portion 7 so that the printed coil sheet70 can be used as a printed wiring board having toroidal printed coilsP.

The toroidal printed coil manufacturing method according to the presentinvention produces the following effects.

That is, in the toroidal printed coil manufacturing method according tothe present invention, the plurality of annular holes and the pluralityof center holes are formed in the insulating substrate, the annular jutsare formed by a plurality of annular portions surrounded by theplurality of annular holes and the plurality of center holes surroundedby these annular holes. With each annular portion taken as an axis, theconductor film is formed at the front-and-rear surfaces andinner-and-outer side surfaces of the annular portion simultaneously andspirally, by which the plurality of toroidal printed coils aremanufactured simultaneously. Therefore, in the printed coil sheet inwhich the plurality of toroidal printed coils have been formed in theinsulating substrate, the plurality of toroidal printed coils can beobtained individually by cutting the individual annular juts off fromthe insulating substrate. Therefore, toroidal printed coils can beobtained extremely simply without requiring much time and labor.

In the prior art manufacturing method, because of the linear shape ofthe through slits 11 as shown in FIG. 8, after cutting tile insulatingsubstrate 10 along the through slits 11 and the cutting lines A, B, C, Dinto so-called chips, a connection-use metal layer can be simply formedat the side surface of each chip. The reason of this is that the cuttingside surface of each chip is flat so that the connection-use metal layercan be simply formed. However, in the case where toroidal printed coilsare manufactured by such a method, in an attempt to form theconnection-use metal layer at the side surface of each chip aftercutting annular chips off from the insulating substrate 10, theconductor film, if formed by printing as an example, would inevitably beformed while the chip-form insulating substrates are rotated in variousangles one by one so as to be opposed to the screen surface of theprinting machine, because the inner-and-outer side surfaces of theannular chips are composite surfaces having concave curved surfaces,convex curved surfaces, or a plurality of planes of different angles ofinclination. Thus, the prior art method would involve much time andlabor. Furthermore, the resulting chips would be small and difficult tohandle. Besides, those chips could not be finely connected to thealready formed conductor film, or might be formed with a positionalshift, resulting in products having resistance values other than desiredvalues.

In contrast to this, with the present invention, before cutting intochips the annular portions each formed with combinations of concavecurved surfaces, convex curved surfaces, or a plurality of planes ofdifferent angles of inclination as described above, a conductor filmthat is necessary as a coil is formed at all the surfaces of frontsurface, rear surface, and inner-and-outer side surfaces of each annularportion. Thus, all the difficulties as described above can be solved.

Working Example

A longitudinally 340 mm, laterally 255 mm copper-clad laminate in whichan 18 μm thick copper foil was cladded on front and rear surfaces of a0.2 mm thick insulating substrate 1 (glass-cloth base epoxy resin madeby Matsushita Electric Works, Ltd.) was prepared. A center hole 3 havingan inner diameter of 5 mm was drilled through this sheet by routerworking, and a 1 mm wide annular hole 2 concentric with the center hole3 was formed so that the annular portion 5 of the annular jut 4 would be6 mm wide. The width of the connecting portion 7 was set to 2 mm. Inthis one insulating substrate 1, 284 annular juts 4 were manufactured,22 pieces longitudinally and 16 pieces laterally, with a pitch of 15 mm.Then, an 18 μm thick copper plating was formed generally entirely on thefront-and-rear surfaces and inner-and-outer side surfaces of the annularportion of each annular jut 4. With the annular portion 5 of eachannular jut 4 taken as an axis, etching resist congruous with theconductor film 6 was formed with a 0.2 mm width of the conductor film 6and a 0.45 mm pitch at the inner-circumferential side surface of theannular portion 5. Next, unnecessary portions of the generally entirelyformed conductor film where no etching resist was formed were removed byetching with ferric chloride. Thereafter the etching resist was flakedoff, by which a conductor film 6 was obtained. Also, in the connectingportion 7, terminals at start and end portions of the coil were formedat a diameter of 0.5 mm on the same plane by etching. Further, afterportions other than the copper foil portions of the coil terminalportions were coated with solder resist, the connecting portion was cutoff by press, by which 294 toroidal printed coils were obtained.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

What is claimed is:
 1. A toroidal printed coil comprising: an insulatingsubstrate having an annular portion, a connection portion, a center holeformed in said annular portion, a base portion, and a C-shaped annularhole arranged such that said annular portion is formed between saidcenter hole and said C-shaped annular hole, and such that said annularportion is connected to said base portion by said connection portion;and a conductor film strip formed around said annular portion of saidinsulating substrate in a helical manner with respect to an annular axisof said annular portion so as to form conductor film on a front surface,a rear surface, an inner surface, and an outer surface of said annularportion.
 2. The toroidal printed coil of claim 1, wherein said conductorfilm strip has a first end terminal at a first end of said conductorfilm strip and a second end terminal at a second end of said conductorfilm strip opposite said first end, said first end terminal and saidsecond end terminal being arranged on said connection portion.
 3. Thetoroidal printed coil of claim 1, wherein said conductor film stripextends an entire length of said annular portion so as to surround saidcenter hole.
 4. The toroidal printed coil of claim 1, wherein an innerperiphery of said annular portion and an outer periphery of said annularportion have a polygonal configuration.
 5. The toroidal printed coil ofclaim 1, wherein a first one of an inner periphery of said annularportion and an outer periphery of said annular portion has a polygonalconfiguration, and a second one of said inner periphery and said outerperiphery has a circular configuration.